This Interactive Research Project Grant (IRPG) will characterize the relationship between menopausal characteristics and sleep in a sample of 430 women: 200 Caucasian, 150 African- American, and 80 Chinese. Although sleep disruptions, insomnia and the incidence of sleep disordered breathing increase in mid- life women, little is known about the relationship between menopause and sleep. The impact of vasomotor symptoms and hormone replacement therapy on sleep suggests that the sleep- menopause relationship is not merely a function of age. A greater understanding of the causes of sleep disturbances in mid- life women is important, given the impact of sleep on mental and physical health. Sleep disturbances are associated with a host of negative health outcomes including losses in productivity and quality of life, psychiatric morbidity, immunosuppression, and increased vulnerability to illness and disease. The study aims of this IRPG are to: 1) characterize sleep disturbances in a large, multi-ethnic sample of mid-life women; 2) characterize relationships among menopausal characteristics and sleep disturbances; 3) evaluate the influence of relevant psychobiological factors on the sleep-menopause relationship; and 4) establish baseline data for a future longitudinal study. Four of seven study sites from the ongoing Study of Women's Health Across the Nation (SWAN) will collaborate to recruit a sample of pre- and peri-menopausal women from the SWAN cohort. Once enrolled in the Sleep Study, participants will begin the protocol at the start of a new menstrual cycle. Ambulatory polysomnography will be conducted in participants' homes during days 1-3 of the protocol. Sleep diary, actigraphy, and event monitor recordings of vasomotor symptom data will be collected throughout the cycle. Data will also include five years of Core SWAN study data on menopausal characteristics (bleeding patterns, vasomotor symptoms, hormone levels) and related psychobiological factors. Regression techniques will be used to model relationships among menopausal characteristics, sleep, and related psychobiological factors. The Pittsburgh site will train study personnel in the use of sleep monitoring equipment and will be responsible for processing, scoring, and archiving all sleep data. All sleep study data, as well as relevant data from the Core SWAN study, will be merged and analyzed by the Michigan site. The Chicago and UC Davis PIS will co-chair the Sleep Study Steering Committee.